The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A transmission is a device that transmits power generated by a vehicle driving source such as an engine by appropriately converting the power into torque desired according to a travelling state. An automatic transmission is a transmission in which a gear is automatically operated according to a traveling speed without a manual operation of a driver.
Typically, an automatic transmission includes a plurality of planetary gear sets in order to transmit power supplied from a vehicle driving source. The automatic transmission includes a one-way clutch preventing a planetary gear set of the plurality of planetary gear sets from rotating in any one direction, the planetary gear set being connected to a transmission input shaft. The one-way clutch can prevent the planetary gear set from rotating in any one direction to permit power from being transmitted in a forward direction while preventing power from being transmitted in a reverse direction.
Torsion occurs in the planetary gear set when torque input to the transmission input shaft from the vehicle driving source is transmitted to the planetary gear set. The one-way clutch can prevent the occurrence of the torsion to stabilize the operation of the planetary gear set, thereby reducing vibration and noise caused by the torsion occurring in the planetary gear set.
However, since the one-way clutch is relatively expensive and heavy, the manufacturing costs and weight of a vehicle are increased. When the one-way clutch is removed, it is impossible either to shift a gear into a specific shift stage using the one-way clutch or to prevent the occurrence of the torsion of the planetary gear set, so that vibration and noise due to the operation of the planetary gear set are increased.
As described in Korean Patent Publication No. 10-2015-0042431, although the function of the one-way clutch for a gear shift (i.e. a function for preventing the reverse rotation of the planetary gear set) can be realized using an alternative technology, it is impossible to prevent the torsion of the planetary gear set. Therefore, it is difficult to remove the one-way clutch.